Jeff,
Whether to include or not include theoretical information is up to you... how do
you want to use the tool? I would point out that Shodor has an applet named
"marbles" at
<
http://www.shodor.org/interactivate/activities/marbles/index.html
>
that is similar to what your applet does (but with only four color choices, and
only one, two, or three marbles per draw); Shodor's gives experimental and
theoretical probabilities.

Similar (but less visual) applets are available in the NCTM "Illuminations" at

This material is based upon work supported by the
National Science Foundation under Grant DUE-0226284.
Any opinions, findings, and conclusions or recommendations
expressed in this material are those of the author(s)
and do not necessarily reflect the views of the
National Science Foundation.